import os
from openpyxl.reader.excel import load_workbook
from openpyxl.drawing.image import Image
import csv

xl_directory = r'<path_to_Excel_directory>'
txt_directory = r'<path_to_text_directory>'

for xl_root, xl_dirs, xl_files in os.walk(xl_directory):
    for xl_file in xl_files:
        if xl_file.endswith('.xlsx'):
            xl_abs_file = os.path.join(xl_root, xl_file)
            wb = load_workbook(xl_abs_file, data_only = True)
            ws = wb.get_sheet_by_name('Filtered')
  
            # Now search for the corresponding text file.
            # Note: if xl_file = '1.xlsx', then xl_file.replace('xlsx', 'txt')
            # returns '1.txt' - the corresponding text file name. If this doesn't
            # hold true, then a different algorithm will be required.
            for txt_root, txt_dirs, txt_files in os.walk(txt_directory):
                for txt_file in txt_files:
                    if txt_file == xl_file.replace('xlsx', 'txt'):
                        fh = open(txt_file, 'r')
                        reader = csv.reader(fh, delimiter = '\t')
                        for row in reader:
                            ws.append(row)
                            wb.save(xl_abs_file)